It is an inherited disorder characterized by a defect in the production of collagen of bones and other tissues. The incidence can range from 1 in 25,000 to 1 in 50,000. Males and females are affected equally.
Brittle Bone Disease Causes
OI is mostly caused by a mutation in genes that regulate collagen production, like COL1A1 / COL1A2, on chromosomes 7 and 17. It can also be due to mutations in the genes CRTAP or LEPRE1.
Most of the cases of brittle bone disease are autosomal dominant, that is, the gene comes from a parent having the disease; some are autosomal recessive, that is, gene is from both parents, neither of whom has the disease. Rarely, it can also be due to a spontaneous mutation in the affected child. Less calcium and poor nutrition are not causative factors.
Signs and Symptoms Of Brittle Bone Disease
Mild variety is often asymptomatic and may go undiagnosed. Eight different types have been identified whose severity ranges from mild fractures to death. Fractures are often multiple due to their brittle nature, accompanied by short stature, blue sclerae, hearing loss, muscle weakness, easy bruising, curvature of spine (scoliosis), breathing problems and brittle teeth which tend to fracture easily. Skin scarring and heart valve disorders may be present.
Diagnosis of OI is based on symptoms and signs. A skin or blood sample can be used to analyse collagen or affected gene. Bone density is found to be low (osteopenia or osteoporosis). Other causes of pathologic fractures need to be excluded, like child abuse, malignancies and low phosphate levels.
Brittle Bone Disease Treatment
As of now, there is no cure for brittle bone disease. However, many patients lead normal lives despite severe deformities. Braces, walking aids, wheelchair, modified home environment can give autonomy to the patient. Smoking and alcohol need to be avoided to reduce bone turnover and keep bones strong and healthy.
Vitamin and mineral supplements have a role to play in keeping bones healthy, and so need to be taken regularly. Bisphosphonates such as pamidronate and alendronate, and supplements of calcium are often prescribed to strengthen the bones and prevent fractures. Hormone replacement therapy can be considered in women.
If fractures occur, they may require intramedullary (in bone marrow) rod fixation to prevent future deformities. Physiotherapy, occupational therapy and swimming are advocated. Growth hormones and gene therapy are also being considered.
Prognosis and Prevention
Prognosis varies from patient to patient depending on the type of the disease. Some may have a normal lifestyle despite the disease while others may die in infancy. Those who survive infancy may succumb later to respiratory failure.
Children of a parent with OI have a 50% chance of contracting the disease. So, genetic counseling is very necessary to prevent the transmission of the disease to future generations.
Prenatal ultrasound and chorionic villus biopsies in first trimester of pregnancy can diagnose the condition in fetus. In those already affected by the disease, several measures can prevent or reduce the severity, such as avoidance of smoking and alcohol, good nutrition and exercise.
Photo Credit: Health-and-living.com/obesity-problems-of-physically-disabled-children/